Overdrive mechanism for automotive power transmission

ABSTRACT

An overdrive mechanism is provided for use in an automatic transmission of the type including a torque converter and a change gear mechanism. The torque converter has a pump impeller obtaining its input from an engine and a turbine runner whose output is applied to a shaft of the change gear mechanism. 
     The overdrive mechanism is disposed between the torque converter and the change gear mechanism and is responsive to the operation of the change gear mechanism. The overdrive mechanism includes a planetary gear train having a sun gear fixed stationary, a carrier operatively responsive to the pump impeller of the torque converter, and a ring gear operatively connected to the sun gear and carrier so that it at all times has output power of a rotational speed greater than that of the engine. An overdrive clutch is provided that connects the shaft of the change gear mechanism to the pump impeller of the torque converter through the ring gear and planetary gear train to thereby by-pass the turbine runner of the torque converter. 
     This device provides for fuel efficiency by eliminating fluid turbulence in the torque converter during this overdrive condition.

BACKGROUND OF THE INVENTION

This invention relates to an overdrive mechanism for use in an automatictransmission of a vehicle such as an automobile.

More particularly, this invention relates to an overdrive mechanism foran automatic transmission of the type incorporating a hydraulic torqueconverter disposed between an engine and a change gear mechanism.

The conventional torque converter of an automatic transmission variesthe turning force automatically and in a smooth and stepless fashion inaccordance with the resistance of the vehicle. However, the conventionaltorque converter is severely limited in a practical sense because ofconsiderable energy loss arising inevitably from fluid friction duringthe passage of fluid through the torque converter or from turbulencecaused by a drastic change in the direction of flow of the fluid. Shoulda conventional overdrive device be employed in this type of automatictransmission, no satisfactory improvement in fuel efficiency can beattained because the engine power is transmitted automatically throughthe torque converter at the time of overdrive.

Accordingly, it is a primary object of this invention to provide a newand improved overdrive mechanism which eliminates the above-describedproblems of the conventional torque converter transmission.

It is a further object of this invention to provide an overdrivemechanism which mechanically transmits the engine power to the changegear mechanism with an improved fuel efficiency by not passing throughthe torque converter.

Another object of this invention is to minimize the fluctuations in therotational force by the torque converter when not required. This usuallyoccurs during a constant high speed operation of the engine for a longperiod such as in overdrive.

Additional objects and advantages of the invention will be set forth inpart in the description which follows, and in part will be obvious fromthe description, or may be learned by practice of the invention. Theobjects and advantages of the invention may be realized and attained bymeans of the instrumentalities and combinations particularly pointed outin the appended claims.

To achieve the foregoing objects and in accordance with the purpose ofthe invention, as embodied and broadly described herein, the overdrivemechanism of this invention is for automatic transmissions of the typeincluding a change gear mechanism having an input shaft, and a torqueconverter having an input element connected to an engine and an outputelement connected to the shaft, and comprises (1) a planetary gear trainincluding (a) a sun gear affixed to the housing of the automatictransmission, (b) a carrier operatively responsive to the input elementof the torque converter, and (c) a ring gear operatively connected tothe sun gear and the carrier to thereby be operatively responsive to theinput element of the torque converter; (2) overdrive clutch meansoperatively connected to the shaft of the change gear mechanism andactivated in response to the operation of the change gear mechanism forengaging the ring gear whereby the shaft of the change gear mechanism isrotated by movement of the ring gear in response to movement of theinput element of the torque converter; and (3) a one-way clutchconnecting the output element of the torque converter to the shaft ofthe change gear mechanism, the one-way clutch decoupling the shaft fromthe output element when the speed of the shaft exceeds that of theoutput element.

The invention consists in the novel parts, constructions, arrangements,combinations and improvements shown and described. The accompanyingdrawings, which are incorporated in and constitute a part of thisspecification, illustrate an embodiment of the invention and, togetherwith the description, serve to explain the principles of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

Of the drawings:

FIG. 1 is a schematic diagram illustrating an embodiment of an automatictransmission employing the teachings of this invention.

FIG. 2 is a sectional view showing the overdrive mechanism of thisinvention.

DETAILED DESCRIPTION OF THE DRAWINGS

Reference will now be made in detail to the present preferred embodimentof the invention, an example of which is illustrated in the accompanyingdrawings.

Referring now to FIG. 1, an automatic transmission, as well known in theart, is schematically shown. A crank shaft 2 of an engine 1 is connectedto a pump impeller 11 of a hydraulic torque converter 10. A turbinerunner 12 of torque converter 10 is operatively connected to an inputshaft 3 of a change gear mechanism 14. A stator 13 is interposed betweenpump impeller 11 and turbine runner 12, and supported by a one-wayclutch 4 so as to rotate only in one direction. The input shaft 3 isfurther connected through a front clutch 5 to an intermediate shaft 6and through a rear clutch 7 to another intermediate shaft 8. Betweenintermediate shafts 6 and 8, and an output shaft 9, is disposed aplanetary gear unit 20.

This planetary gear unit 20 consists of first and second sun gears 21and 22 which are respectively mounted on the intermediate shafts 6 and8. A short pinion 23 engages with second sun gear 22, and a long pinion25 engages with short pinion 23, first sun gear 21 and a gear 24 ofoutput shaft 9. A carrier 26 rotatably supports short and long pinions23 and 25.

A combined first and reverse brake 27 and a one-way clutch 28 aremounted on carrier 26. A second brake 29 is mounted on a rear clutchdrum 7a and is made integral with second sun gear 22. The constructionof the above-described change gear mechanism is more fully disclosed inU.S. Pat. No. 3,714,847, assigned to the same firm as is thisapplication.

In accordance with the present invention, an overdrive mechanism 30 isprovided in the automatic transmission of the above-described typebetween the torque converter 10 and the change gear mechanism 14.

As here embodied, and as best seen in FIG. 2, one-way clutch 31 isprovided between the input shaft 3 and an external surface 12a of thecasing of the turbine runner 12 in such a fashion that turbine runner 12is engaging the clutch only when turbine runner 12 is operating at ahigher speed than input shaft 3. An internal surface 11a of the casingof pump impeller 11 is connected mechanically through torsional damper40 to an intermediate shaft 32 which is disposed coaxially outside ofthe input shaft 3. Between intermediate shaft 32 and input shaft 3 ispositioned a single planetary gear train 50, a one-way clutch 57 and anoverdrive clutch 60.

Preferably, torsional damper 40 comprises a connection plate 42 adaptedto the internal surface 11a of the casing of pump impeller 11.Connection plate 42 has a number of teeth 41 defined on the peripherythereof. A flange 43 extends from the vicinity of connection plate 42through the spacing between turbine runner 12 and stator 13, and is thenconnected to intermediate shaft 32. Engaging means such as plate 44 ismounted onto the outer peripheral section 43a of flange 43 and engagesintegrally with teeth 41 in a direction of rotation. A torsion spring 45is interposed between teeth 41 and engaging means 44 so as to mitigatethe shock at the time of power transmission. As can be seen from thisassembly, torsional damper 40 functions to mechanically transmit thepower from pump impeller 11 to intermediate shaft 32.

Preferably, single planetary gear train 50 is comprised of a ring gear51, a sun gear 53 fixed to the casing 52 of the automatic transmission,a pinion 54 which engages both ring gear 51 and sun gear 53, and acarrier 56 which is operatively connected to the intermediate shaft 32and supports rotatably the pinion 54 through a needle roller 55. Withthis arrangement, the single planetary gear train 50 is operable tocontinuously turn ring gear 51 with greater rotational speed than thatof the engine provided through carrier 56.

Overdrive clutch 60 may comprise the same construction with those of theaforementioned clutches 5 and 7. A disc 65 mounted on a hub 64 carryingthe ring gear 51 is positioned between a plate 62 and a flange 63 thatare secured to a drum 61. Drum 61 in turn is operatively connected toshaft 3 of the change gear mechanism. When a piston 66 located withindrum 61 is hydraulically actuated against the force of a return spring67, plate 62 and flange 63 engage disc 65 to provide an integralcoupling between ring gear 51 and shaft 3. It is preferred that one-wayclutch 57 be located between hub 64 having ring gear 51 and the inputshaft 3, and that it effect engaging action when the rotational speed ofinput shaft 3 exceeds that of ring gear 51.

When the vehicle is being run by engine power, the power of crank shaft2 of the engine is transmitted hydraulically from pump impeller 11 oftorque converter 10 to turbine runner 12. Turbine runner 12 in turnprovides an input to shaft 3 through one-way clutch 31 since clutch 31effects engaging action with turbine runner 12 when turbine runner 12 isrotating at a higher speed than the input shaft 3. Simultaneously, thepower of pump impeller 11 of torque converter 10 is applied to carrier56 of single planetary gear train 50 through torsional damper 40 andintermediate shaft 32. Carrier 56 turns pinion 54 about the fixed sungear 53 so that ring gear 51 rotates at a higher speed than that of theengine. Since overdrive clutch 60 and one-way clutch 57 are not actuatedduring this time, they are not in an engaging position with ring gear51.

During operation of the automatic transmission, the power of input shaft3 is input to the drum side of front clutch 5 and the hub side of rearclutch 7. This power is further transmitted to first sun gear 21 ofplanetary gear unit 20 through the intermediate shaft 6 by means of theengaging action of front clutch 5. If carrier 26 is locked by the actionof one-way clutch 28 or the combined first and reverse brake 27, outputshaft 9 is furnished with the output of the first or low speed runningcondition of a maximum gear ratio. Likewise, if second sun gear 22 islocked by the action of second brake 29, output shaft 9 is furnishedwith the second speed running condition of a gear ratio that is smallerthan that of the first speed. Further, if the engine power is also inputto second sun gear 22 through intermediate shaft 8 be engaging action offront clutch 5, the planetary gear unit 20 is integrated so that a highspeed rotation of input shaft 3 is transmitted as such to output shaft9. In this event, a shift to the third speed running condition occurs.

However, when the power of input shaft 3 is input to second sun gear 22by the engaging action of rear clutch 7, and carrier 26 is locked by theaction of the combined first and reverse brake 27, output shaft 9 issupplied with a reversed speed running condition.

Three forward and one reverse speeds are possible by selectiveactivation of clutches 5 and 7, brakes 27 and 29, and one-way clutch 28.When, under the third speed condition, input and output shafts 3 and 9are connected directly with each other by the action of the two clutches5 and 7, the overdrive clutch 60 is activated to connect ring gear 51with input shaft 3. Ring gear 51 up to now has been rotating in singleplanetary gear train 50 in an idling condition. By this engagement, thehigher rotational speed of ring gear 51 is transmitted to input shaft 3so that input shaft 3 is caused to rotate with a larger number ofrevolutions than that of the engine.

In this manner, one-way clutch 31 disengages torque runner 12 from inputshaft 3 as input shaft 3 comes to a higher speed. Engine powertransmitted hydraulically through a fluid from pump impeller 11 oftorque converter 10 to turbine runner 12 is not transmitted to inputshaft 3. Instead, the engine power is transmitted mechanically from pumpimpeller 11 to intermediate shaft 32, and into planetary gear train 50.Since the higher rotational speed of ring gear 51 is taken up at inputshaft 3, the power is subsequently transmitted directly to shaft 9, thusestablishing the overdrive condition.

In a vehicle wheel drive situation during any of the running conditionspreviously mentioned, one-way clutch 31 disengages torque runner 12 frominput shaft 3. Therefore, the transmission of power is prevented frominput shaft 3 to turbine runner 12 of torque converter 10. However, ringgear 51 is rotating at a high speed by the driving power which is beingmechanically transmitted from pump impeller 11. As the differencebetween the number of rotations of input shaft 3 driven by the wheelsbecomes higher than that of ring gear 51, one-way clutch 57 is actuated.

As a result of this situation, one-way clutch 57 effects engaging actionbetween ring gear 51 and input shaft 3. By doing so, the power of inputshaft 3 is transmitted through one-way clutch 57, single planetary geartrain 50, intermediate shaft 32, and pump impeller 11 to the engine.This establishes a braking force on the engine. In an overdrivecondition, an engine brake can always be effectuated since the drivingpower is transmitted from the outset without resorting to one-way clutch31, and since ring gear 51 and input shaft 3 are connected with eachother through overdrive clutch 60.

As shown in this preferred embodiment of the invention, transmission ofpower is possible without passing through torque converter 10 at thetime of overdrive. Accordingly, the poor performance of a torqueconverter is significantly minimized during an overdrive condition, andfuel efficiency is greatly improved. At the same time, the effect ofmultiplying the engine rotational speed to the change gear mechanism isacccomplished.

In accordance with the present invention, transmission of power isquickly and easily changeable by mere manipulation of overdrive clutch60 from the ordinary transmission through torque converter 10 to amechanical transmission by-passing torque converter 10. This phenomenoneliminates the use of a turning element effecting a relative rotationinside the torque converter 10 so that loss of energy due to agitationof the fluid by such a turning element is eliminated. This furtherensures a highly efficient working condition of torque converter 10.

It should be noted that the overdrive mechanism 30 of this invention canbe applied to a change gear mechanism other than the one described inthis preferred embodiment. Additionally, the positioning of one-wayclutch 31 and torsional damper 40 need not be limited specifically tothat illustrated in this preferred embodiment.

It will be apparent to those skilled in the art that variousmodifications and variations could be made in the overdrive device ofthe invention without departing from the scope or spirit of theinvention.

What is claimed is:
 1. An improved automatic transmission with an overdrive device for an engine having a driving member comprising:a. a change gear mechanism having:i. an input shaft, ii. a planetary gear train, and iii. a plurality of frictional engagement means for interconnecting said input shaft to said planetary gear train; b. a torque converter having:i. a pump impeller connected to the driving member of the engine, ii. a turbine runner connected to said input shaft of said change gear mechanism, iii. a stator located between said pump impeller and said turbine runner, and iv. a converter housing for enclosing said pump impeller, said turbine runner, and said stator in fluid flow relationship therein; c. an overdrive device positioned outside of said converter housing between said torque converter and said change gear mechanism, said device having:i. an overdrive gear train including a sun gear affixed to the housing of said automatic transmission, a carrier responsive to said pump impeller, a ring gear, and a pinion rotatably supported by said carrier and engaging said ring gear and said sun gear, said ring gear thereby being responsive to said pump impeller and rotating at a higher speed than said pump impeller, ii. overdrive clutch means connected to said input shaft of said change gear mechanism outside of said converter housing and activated in response to the operation of said change gear mechanism for engaging said ring gear whereby said input shaft of said change gear mechanism rotates with said ring gear in response to movement of said pump impeller, and iii. an intermediate shaft rotatably and co-axially disposed around said input shaft of said change gear mechanism having a first end connected to said pump impeller in said converter housing and a second end extending out of said converter housing and connected to said carrier; and e. a one-way clutch connecting said turbine runner to said input shaft, said one-way clutch decoupling said shaft from said turbine runner when the speed of said input shaft exceeds that of said turbine runner.
 2. The improved transmission of claim 1 wherein said overdrive clutch means is integrally attached to said input shaft of said change gear mechanism for rotation therewith.
 3. The improved transmission of claim 1 further including a torsional damper, said damper comprising (i) a connection plate formed upon the internal surface of said pump impeller, said plate having teeth on the periphery thereof, (ii) a flange connected to said first end of said intermediate shaft, (iii) means mounted on the periphery of said flange for engaging the teeth of said connection plate, and (iv) a torsion spring interposed between said teeth and said engaging means so as to mitigate shock during power transmission.
 4. The improved transmission of claim 1 wherein said overdrive clutch means includes a clutch having a drum connected to said shaft of said change gear mechanism, for rotation therewith, a plate secured to said drum, a piston within said drum for hydraulic operation in response to actuation by the change gear mechanism, a flange secured to said drum; and said overdrive device further including a hub for carrying said ring gear, said hub having a disc mounted thereon and positioned between said plate and said flange of said drum so that when said piston is actuated, the plate and flange engage said disc to thereby engage said ring gear with said clutch.
 5. The improved transmission of claim 1 wherein said overdrive device further includes a one-way clutch located adjacent to said hub for effecting engaging action with said hub when the rotational speed of said input shaft of said change gear mechanism exceeds that of said ring gear.
 6. The improved transmission of claim 4 wherein said overdrive gear train is positioned immediately adjacent said converter housing and said overdrive clutch means is positioned adjacent said overdrive gear train, said overdrive gear train and overdrive clutch means being outside the fluid flow of said torque converter and in concentric relationship with said input shaft of said change gear mechanism. 